The preparation and service of food in commercial quantities is a common task in many institutions. For instance, restaurants, hospitals, schools, prisons and the like, must supply food daily to a relatively large number of people which results in the need for the daily cleaning of a substantial quantity of dishware. Such systems can be expensive to operate.
In the conventional commercial dishwashing system, a rack, or a flight type conveyor having integral compartments, is loaded with a set of dishware. The dishware is then conveyed through a wash chamber. In the wash chamber, cleaning fluid and rinse water are sprayed onto the dishware for the purpose of cleaning the dishware. The dishware exits the dishwasher and is removed from the rack ready for reuse.
A satisfactory dishwashing system must accomplish the goals of cleaning and sanitizing the dishware. As the dishware advances through the wash chamber of the dishwasher, many of the surfaces to be cleaned are shielded from the direct application of a cleaning fluid stream due to the shapes and location in the rack. In addition, corners and crevices on the dishware often further prevent the dishware from being completely cleaned. Spots or streaks on the dishware as it exits the dishwasher indicate that the dishwashing system has failed to meet its goals.
The cleaning function is accomplished by directing as much cleaning fluid as possible toward each single piece of dishware. The greater the area of the dishware that is directly hit by a stream of cleaning fluid, the more likely that all soil will be removed from the dishware. In addition, the more powerful the stream of cleaning fluid, and the greater length of time the stream is directed toward the dishware, the more likely the dishware will be completely cleaned.
The sanitizing function is accomplished by heating a sufficient quantity of the cleaning fluid sprayed on the dishware to a temperature of 155.degree. F. and a sufficient quantity of rinse water to 180.degree. F. Conventionally, the sanitizing function is initiated in a wash zone in the wash chamber and is completed in a rinse zone which may occur separate from the wash chamber. The hot cleaning fluid also helps in the cleaning function, since the soil is more readily removed from the dishware when it is at an elevated temperature.
The designer of a commercially-satisfactory dishwashing system has difficulties in simultaneously accomplishing the cleaning function and initiating the sanitizing function because each has requirements which run counter to the other. For instance, the greater the amount of cleaning fluid sprayed in the wash chamber to accomplish the cleaning function, the greater the heat loss in the wash chamber. Tests have shown that the mist and wind created inside the wash chamber lower the temperature of the cleaning fluid and internal temperature of the wash chamber due to evaporation of cleaning fluid water. To compensate for this heat loss, electric or steam heating elements must be added in the wash chamber to add heat to the recirculating cleaning fluid. Of course, to further heat the cleaning fluid more energy, and fuel cost, must be incurred. Greater water consumption also increases operating costs.
Therefore, a designer of a commercial dishwashing system must take into account several variables which tend to work against each other. The amount of water supplied per a given period of time must be addressed. The temperature to which the cleaning fluid is initially heated and subsequently reheated by heating elements located in the wash chamber affects energy costs and must be addressed. The hydraulic pressure which is applied to the cleaning fluid affects energy costs and must be addressed. The ability to prevent heat dissipation within the wash chamber and the ability to maintain high enough temperatures to initiate sanitizing of the dishware must be addressed. The ability to have a stream of spray which reaches a large portion of the surface of the dishware, the pattern of the spray, and the direction of the spray must be determined. The size and shape of the nozzles, including the size of the apertures, must be determined. A proper combination of the above variables is needed in order to maximize cleaning and sanitizing efficiency, and to minimize the cost while increasing the ease of operation.
U.S. Pat. No. 5,131,419 issued to Roberts illustrates a dishwasher designed for cleaning dishware located on racks. The dishwasher cleans the dishes by spraying fluid from above and below the dishes at a washing temperature of 180.degree. F. At a separate period in the cleaning cycle, the dishwasher cleans utensils, such as forks and spoons, by directing a substantially horizontal spray toward the utensils at a wash temperature of 180.degree. F. The Roberts '419 patent does not suggest simultaneously spraying cleaning fluid from above, below and horizontally across the dishware.
The assignee of the present invention has provided dishwashing equipment with simultaneous cleaning fluid spray from above, below and to the side of the dishware. However, to further advance the art of commercial dishwashing systems, an improved dishwasher is needed which provides a multi-spraying system and which can maintain higher internal wash chamber temperatures and eliminate splashing of cleaning fluid outside of the wash chamber.
Although the aforementioned dishwashers may function satisfactorily for their intended purposes, there is a need for a dishwasher engineered to maximize cleaning efficiency. The dishwasher should be able to direct streams of cleaning fluid simultaneously from above and below the dishware as well as horizontally across the dishware to maximize the cleaning function of the dishwasher. At the same time, the dishwasher should minimize water consumption, spraying and recirculation so as to allow the cleaning fluid and internal wash chamber temperature to remain at or above 155.degree. F. Furthermore, the dishwasher should minimize splashing, should be easy to use, inexpensive to manufacture, and require a minimum of energy to operate.